MadeEasy Workbook: Databases - Er Diagram

Question

The minimum number of tables needed to represent M,N,P,R1,R2 is …

The given ans is 2.

I think the ans should be 3.

Comments

I think

MR1P --->M1 & P1 as PK

NR2----->P1 N1 as PK

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Why merge M and P... there can be null values in the final relation..!!

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They asked min number of tables, there can be null values in that case

Answer 1

Yes it is possible such that

R1 (M1,M2,M3) and R2 (P1,P2,N1, N2).

I also think the answer is 3 but this explanation given Made easy test series. Because the second relationship is identifying relationships .

Comments

Bro, even if the second relationship is identifying relationship, it does not ensure the merging of P and N - all it can ensure is merging of R2 and N.

Please provide me with any standard references like a book or some instructors blog etc.

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@ Harsh

https://db.grussell.org/section006.html

Subsumes the entity concept.

Answer 2

https://gateoverflow.in/390/gate-cse-2008-question-82

inswer is 3